THE DEVELOPMENT OF ARTICULAR-CARTILAGE .2. THE SPATIAL AND TEMPORAL PATTERNS OF GLYCOSAMINOGLYCANS AND SMALL LEUCINE-RICH PROTEOGLYCANS

Articular cartilage is both morphologically and biochemically heteroge neous. Its susceptibility to degenerative diseases such as arthritis a nd its limited repair capacity has made cartilage the focus of intense study; surprisingly, little is known of its development. Using a pane l of specific antibodies, we have documented the temporal and spatial patterns of the small leucine-rich proteoglycans fibomodulin, decorin and biglycan in the developing knee cartilage of the marsupial South A merican opposum (Monodelphis domestica) from parturition to adulthood. The major proteoglycan of cartilage, aggrecan, can be substituted wit h a variety of isomers of chondroitin sulphate (CS) and keratan sulpha te (KS) glycosaminoglycans. Consequently, we have used monoclonal anti bodies to determine the distribution of the chondroitinase generated e pitopes of CS isomers (Delta di-6S and Delta di-4S oligosaccharide 'st ubs'). Other monoclonal antibodies (3B3[-], 7D4) were used to investig ate temporal changes in the expression of specific sulphation patterns within native chondroitin sulphate chains in addition to keratan sulp hate chains (5D4). We found the distributions of the small proteoglyca ns (PGs) to be highly dynamic during development. Both fibromodulin an d biglycan appeared to specifically label early articular cartilage as opposed to epiphyseal or growth plate cartilage. All 3 small PGs beco me preferentially distributed to the upper half of the adult articular cartilage depth. Similarly, Delta di-6S, Delta di-4S oligosaccharide 'stubs', RS and epitope 7D4 were variably distributed during developme nt but all were again preferentially located to the upper depth of the mature tissue. The epitope recognised by antibody 3B3[-] was extensiv ely distributed in the neonate, but became more restricted to hypertro phic chondrocytes by day 19. It was not detected in the adult tissue. These data suggest that in Monodelphis, proteoglycans are preferential ly synthesised and elaborated in the upper half of the tissue depth an d contrasts with the patterns observed in eutherian mammals. The data also pose questions as to the functional significance of these molecul es within the tissues and to the idea that global patterns of matrix c omponents exist in mammalian articular cartilages.